gcc/sibcall.c

   1 /* Generic sibling call optimization support
   2    Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
   3
   4 This file is part of GNU CC.
   5
   6 GNU CC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU CC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU CC; see the file COPYING.  If not, write to
  18 the Free Software Foundation, 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23
  24 #include "rtl.h"
  25 #include "regs.h"
  26 #include "function.h"
  27 #include "hard-reg-set.h"
  28 #include "flags.h"
  29 #include "insn-config.h"
  30 #include "recog.h"
  31 #include "basic-block.h"
  32 #include "output.h"
  33 #include "except.h"
  34
  35 static int identify_call_return_value   PARAMS ((rtx, rtx *, rtx *));
  36 static rtx skip_copy_to_return_value    PARAMS ((rtx));
  37 static rtx skip_use_of_return_value     PARAMS ((rtx, enum rtx_code));
  38 static rtx skip_stack_adjustment        PARAMS ((rtx));
  39 static rtx skip_pic_restore             PARAMS ((rtx));
  40 static rtx skip_jump_insn               PARAMS ((rtx));
  41 static int call_ends_block_p            PARAMS ((rtx, rtx));
  42 static int uses_addressof               PARAMS ((rtx));
  43 static int sequence_uses_addressof      PARAMS ((rtx));
  44 static void purge_reg_equiv_notes       PARAMS ((void));
  45 static void purge_mem_unchanging_flag   PARAMS ((rtx));
  46
  47 /* Examine a CALL_PLACEHOLDER pattern and determine where the call's
  48    return value is located.  P_HARD_RETURN receives the hard register
  49    that the function used; P_SOFT_RETURN receives the pseudo register
  50    that the sequence used.  Return non-zero if the values were located.  */
  51
  52 static int
  53 identify_call_return_value (cp, p_hard_return, p_soft_return)
  54      rtx cp;
  55      rtx *p_hard_return, *p_soft_return;
  56 {
  57   rtx insn, set, hard, soft;
  58
  59   insn = XEXP (cp, 0);
  60   /* Search backward through the "normal" call sequence to the CALL insn.  */
  61   while (NEXT_INSN (insn))
  62     insn = NEXT_INSN (insn);
  63   while (GET_CODE (insn) != CALL_INSN)
  64     insn = PREV_INSN (insn);
  65
  66   /* Assume the pattern is (set (dest) (call ...)), or that the first
  67      member of a parallel is.  This is the hard return register used
  68      by the function.  */
  69   if (GET_CODE (PATTERN (insn)) == SET
  70       && GET_CODE (SET_SRC (PATTERN (insn))) == CALL)
  71     hard = SET_DEST (PATTERN (insn));
  72   else if (GET_CODE (PATTERN (insn)) == PARALLEL
  73            && GET_CODE (XVECEXP (PATTERN (insn), 0, 0)) == SET
  74            && GET_CODE (SET_SRC (XVECEXP (PATTERN (insn), 0, 0))) == CALL)
  75     hard = SET_DEST (XVECEXP (PATTERN (insn), 0, 0));
  76   else
  77     return 0;
  78
  79   /* If we didn't get a single hard register (e.g. a parallel), give up.  */
  80   if (GET_CODE (hard) != REG)
  81     return 0;
  82
  83   /* Stack adjustment done after call may appear here.  */
  84   insn = skip_stack_adjustment (insn);
  85   if (! insn)
  86     return 0;
  87
  88   /* Restore of GP register may appear here.  */
  89   insn = skip_pic_restore (insn);
  90   if (! insn)
  91     return 0;
  92
  93   /* If there's nothing after, there's no soft return value.  */
  94   insn = NEXT_INSN (insn);
  95   if (! insn)
  96     return 0;
  97
  98   /* We're looking for a source of the hard return register.  */
  99   set = single_set (insn);
 100   if (! set || SET_SRC (set) != hard)
 101     return 0;
 102
 103   soft = SET_DEST (set);
 104   insn = NEXT_INSN (insn);
 105
 106   /* Allow this first destination to be copied to a second register,
 107      as might happen if the first register wasn't the particular pseudo
 108      we'd been expecting.  */
 109   if (insn
 110       && (set = single_set (insn)) != NULL_RTX
 111       && SET_SRC (set) == soft)
 112     {
 113       soft = SET_DEST (set);
 114       insn = NEXT_INSN (insn);
 115     }
 116
 117   /* Don't fool with anything but pseudo registers.  */
 118   if (GET_CODE (soft) != REG || REGNO (soft) < FIRST_PSEUDO_REGISTER)
 119     return 0;
 120
 121   /* This value must not be modified before the end of the sequence.  */
 122   if (reg_set_between_p (soft, insn, NULL_RTX))
 123     return 0;
 124
 125   *p_hard_return = hard;
 126   *p_soft_return = soft;
 127
 128   return 1;
 129 }
 130
 131 /* If the first real insn after ORIG_INSN copies to this function's
 132    return value from RETVAL, then return the insn which performs the
 133    copy.  Otherwise return ORIG_INSN.  */
 134
 135 static rtx
 136 skip_copy_to_return_value (orig_insn)
 137      rtx orig_insn;
 138 {
 139   rtx insn, set = NULL_RTX;
 140   rtx hardret, softret;
 141
 142   /* If there is no return value, we have nothing to do.  */
 143   if (! identify_call_return_value (PATTERN (orig_insn), &hardret, &softret))
 144     return orig_insn;
 145
 146   insn = next_nonnote_insn (orig_insn);
 147   if (! insn)
 148     return orig_insn;
 149
 150   set = single_set (insn);
 151   if (! set)
 152     return orig_insn;
 153
 154   /* The destination must be the same as the called function's return
 155      value to ensure that any return value is put in the same place by the
 156      current function and the function we're calling.
 157
 158      Further, the source must be the same as the pseudo into which the
 159      called function's return value was copied.  Otherwise we're returning
 160      some other value.  */
 161
 162 #ifndef OUTGOING_REGNO
 163 #define OUTGOING_REGNO(N) (N)
 164 #endif
 165
 166   if (SET_DEST (set) == current_function_return_rtx
 167       && REG_P (SET_DEST (set))
 168       && OUTGOING_REGNO (REGNO (SET_DEST (set))) == REGNO (hardret)
 169       && SET_SRC (set) == softret)
 170     return insn;
 171
 172   /* It did not look like a copy of the return value, so return the
 173      same insn we were passed.  */
 174   return orig_insn;
 175 }
 176
 177 /* If the first real insn after ORIG_INSN is a CODE of this function's return
 178    value, return insn.  Otherwise return ORIG_INSN.  */
 179
 180 static rtx
 181 skip_use_of_return_value (orig_insn, code)
 182      rtx orig_insn;
 183      enum rtx_code code;
 184 {
 185   rtx insn;
 186
 187   insn = next_nonnote_insn (orig_insn);
 188
 189   if (insn
 190       && GET_CODE (insn) == INSN
 191       && GET_CODE (PATTERN (insn)) == code
 192       && (XEXP (PATTERN (insn), 0) == current_function_return_rtx
 193           || XEXP (PATTERN (insn), 0) == const0_rtx))
 194     return insn;
 195
 196   return orig_insn;
 197 }
 198
 199 /* If the first real insn after ORIG_INSN adjusts the stack pointer
 200    by a constant, return the insn with the stack pointer adjustment.
 201    Otherwise return ORIG_INSN.  */
 202
 203 static rtx
 204 skip_stack_adjustment (orig_insn)
 205      rtx orig_insn;
 206 {
 207   rtx insn, set = NULL_RTX;
 208
 209   insn = next_nonnote_insn (orig_insn);
 210
 211   if (insn)
 212     set = single_set (insn);
 213
 214   if (insn
 215       && set
 216       && GET_CODE (SET_SRC (set)) == PLUS
 217       && XEXP (SET_SRC (set), 0) == stack_pointer_rtx
 218       && GET_CODE (XEXP (SET_SRC (set), 1)) == CONST_INT
 219       && SET_DEST (set) == stack_pointer_rtx)
 220     return insn;
 221
 222   return orig_insn;
 223 }
 224
 225 /* If the first real insn after ORIG_INSN sets the pic register,
 226    return it.  Otherwise return ORIG_INSN.  */
 227
 228 static rtx
 229 skip_pic_restore (orig_insn)
 230      rtx orig_insn;
 231 {
 232   rtx insn, set = NULL_RTX;
 233
 234   insn = next_nonnote_insn (orig_insn);
 235
 236   if (insn)
 237     set = single_set (insn);
 238
 239   if (insn && set && SET_DEST (set) == pic_offset_table_rtx)
 240     return insn;
 241
 242   return orig_insn;
 243 }
 244
 245 /* If the first real insn after ORIG_INSN is a jump, return the JUMP_INSN.
 246    Otherwise return ORIG_INSN.  */
 247
 248 static rtx
 249 skip_jump_insn (orig_insn)
 250      rtx orig_insn;
 251 {
 252   rtx insn;
 253
 254   insn = next_nonnote_insn (orig_insn);
 255
 256   if (insn
 257       && GET_CODE (insn) == JUMP_INSN
 258       && any_uncondjump_p (insn))
 259     return insn;
 260
 261   return orig_insn;
 262 }
 263 \f
 264 /* Using the above functions, see if INSN, skipping any of the above,
 265    goes all the way to END, the end of a basic block.  Return 1 if so.  */
 266
 267 static int
 268 call_ends_block_p (insn, end)
 269      rtx insn;
 270      rtx end;
 271 {
 272   /* END might be a note, so get the last nonnote insn of the block.  */
 273   end = next_nonnote_insn (PREV_INSN (end));
 274
 275   /* If the call was the end of the block, then we're OK.  */
 276   if (insn == end)
 277     return 1;
 278
 279   /* Skip over copying from the call's return value pseudo into
 280      this function's hard return register and if that's the end
 281      of the block, we're OK.  */
 282   insn = skip_copy_to_return_value (insn);
 283   if (insn == end)
 284     return 1;
 285
 286   /* Skip any stack adjustment.  */
 287   insn = skip_stack_adjustment (insn);
 288   if (insn == end)
 289     return 1;
 290
 291   /* Skip over a CLOBBER of the return value as a hard reg.  */
 292   insn = skip_use_of_return_value (insn, CLOBBER);
 293   if (insn == end)
 294     return 1;
 295
 296   /* Skip over a USE of the return value (as a hard reg).  */
 297   insn = skip_use_of_return_value (insn, USE);
 298   if (insn == end)
 299     return 1;
 300
 301   /* Skip over a JUMP_INSN at the end of the block.  If that doesn't end the
 302      block, the original CALL_INSN didn't.  */
 303   insn = skip_jump_insn (insn);
 304   return insn == end;
 305 }
 306
 307 /* Scan the rtx X for ADDRESSOF expressions or
 308    current_function_internal_arg_pointer registers.
 309    Return nonzero if an ADDRESSOF or current_function_internal_arg_pointer
 310    is found outside of some MEM expression, else return zero.  */
 311
 312 static int
 313 uses_addressof (x)
 314      rtx x;
 315 {
 316   RTX_CODE code;
 317   int i, j;
 318   const char *fmt;
 319
 320   if (x == NULL_RTX)
 321     return 0;
 322
 323   code = GET_CODE (x);
 324
 325   if (code == ADDRESSOF || x == current_function_internal_arg_pointer)
 326     return 1;
 327
 328   if (code == MEM)
 329     return 0;
 330
 331   /* Scan all subexpressions. */
 332   fmt = GET_RTX_FORMAT (code);
 333   for (i = 0; i < GET_RTX_LENGTH (code); i++, fmt++)
 334     {
 335       if (*fmt == 'e')
 336         {
 337           if (uses_addressof (XEXP (x, i)))
 338             return 1;
 339         }
 340       else if (*fmt == 'E')
 341         {
 342           for (j = 0; j < XVECLEN (x, i); j++)
 343             if (uses_addressof (XVECEXP (x, i, j)))
 344               return 1;
 345         }
 346     }
 347   return 0;
 348 }
 349
 350 /* Scan the sequence of insns in SEQ to see if any have an ADDRESSOF
 351    rtl expression or current_function_internal_arg_pointer occurences
 352    not enclosed within a MEM.  If an ADDRESSOF expression or
 353    current_function_internal_arg_pointer is found, return nonzero, otherwise
 354    return zero.
 355
 356    This function handles CALL_PLACEHOLDERs which contain multiple sequences
 357    of insns.  */
 358
 359 static int
 360 sequence_uses_addressof (seq)
 361      rtx seq;
 362 {
 363   rtx insn;
 364
 365   for (insn = seq; insn; insn = NEXT_INSN (insn))
 366     if (INSN_P (insn))
 367       {
 368         /* If this is a CALL_PLACEHOLDER, then recursively call ourselves
 369            with each nonempty sequence attached to the CALL_PLACEHOLDER.  */
 370         if (GET_CODE (insn) == CALL_INSN
 371             && GET_CODE (PATTERN (insn)) == CALL_PLACEHOLDER)
 372           {
 373             if (XEXP (PATTERN (insn), 0) != NULL_RTX
 374                 && sequence_uses_addressof (XEXP (PATTERN (insn), 0)))
 375               return 1;
 376             if (XEXP (PATTERN (insn), 1) != NULL_RTX
 377                 && sequence_uses_addressof (XEXP (PATTERN (insn), 1)))
 378               return 1;
 379             if (XEXP (PATTERN (insn), 2) != NULL_RTX
 380                 && sequence_uses_addressof (XEXP (PATTERN (insn), 2)))
 381               return 1;
 382           }
 383         else if (uses_addressof (PATTERN (insn))
 384                  || (REG_NOTES (insn) && uses_addressof (REG_NOTES (insn))))
 385           return 1;
 386       }
 387   return 0;
 388 }
 389
 390 /* Remove all REG_EQUIV notes found in the insn chain.  */
 391
 392 static void
 393 purge_reg_equiv_notes ()
 394 {
 395   rtx insn;
 396
 397   for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
 398     {
 399       while (1)
 400         {
 401           rtx note = find_reg_note (insn, REG_EQUIV, 0);
 402           if (note)
 403             {
 404               /* Remove the note and keep looking at the notes for
 405                  this insn.  */
 406               remove_note (insn, note);
 407               continue;
 408             }
 409           break;
 410         }
 411     }
 412 }
 413
 414 /* Clear RTX_UNCHANGING_P flag of incoming argument MEMs.  */
 415
 416 static void
 417 purge_mem_unchanging_flag (x)
 418      rtx x;
 419 {
 420   RTX_CODE code;
 421   int i, j;
 422   const char *fmt;
 423
 424   if (x == NULL_RTX)
 425     return;
 426
 427   code = GET_CODE (x);
 428
 429   if (code == MEM)
 430     {
 431       if (RTX_UNCHANGING_P (x)
 432           && (XEXP (x, 0) == current_function_internal_arg_pointer
 433               || (GET_CODE (XEXP (x, 0)) == PLUS
 434                   && XEXP (XEXP (x, 0), 0) ==
 435                      current_function_internal_arg_pointer
 436                   && GET_CODE (XEXP (XEXP (x, 0), 1)) == CONST_INT)))
 437         RTX_UNCHANGING_P (x) = 0;
 438       return;
 439     }
 440
 441   /* Scan all subexpressions. */
 442   fmt = GET_RTX_FORMAT (code);
 443   for (i = 0; i < GET_RTX_LENGTH (code); i++, fmt++)
 444     {
 445       if (*fmt == 'e')
 446         purge_mem_unchanging_flag (XEXP (x, i));
 447       else if (*fmt == 'E')
 448         for (j = 0; j < XVECLEN (x, i); j++)
 449           purge_mem_unchanging_flag (XVECEXP (x, i, j));
 450     }
 451 }
 452
 453 /* Replace the CALL_PLACEHOLDER with one of its children.  INSN should be
 454    the CALL_PLACEHOLDER insn; USE tells which child to use.  */
 455
 456 void
 457 replace_call_placeholder (insn, use)
 458      rtx insn;
 459      sibcall_use_t use;
 460 {
 461   if (use == sibcall_use_tail_recursion)
 462     emit_insns_before (XEXP (PATTERN (insn), 2), insn);
 463   else if (use == sibcall_use_sibcall)
 464     emit_insns_before (XEXP (PATTERN (insn), 1), insn);
 465   else if (use == sibcall_use_normal)
 466     emit_insns_before (XEXP (PATTERN (insn), 0), insn);
 467   else
 468     abort();
 469
 470   /* Turn off LABEL_PRESERVE_P for the tail recursion label if it
 471      exists.  We only had to set it long enough to keep the jump
 472      pass above from deleting it as unused.  */
 473   if (XEXP (PATTERN (insn), 3))
 474     LABEL_PRESERVE_P (XEXP (PATTERN (insn), 3)) = 0;
 475
 476   /* "Delete" the placeholder insn. */
 477   PUT_CODE (insn, NOTE);
 478   NOTE_SOURCE_FILE (insn) = 0;
 479   NOTE_LINE_NUMBER (insn) = NOTE_INSN_DELETED;
 480 }
 481
 482 /* Given a (possibly empty) set of potential sibling or tail recursion call
 483    sites, determine if optimization is possible.
 484
 485    Potential sibling or tail recursion calls are marked with CALL_PLACEHOLDER
 486    insns.  The CALL_PLACEHOLDER insn holds chains of insns to implement a
 487    normal call, sibling call or tail recursive call.
 488
 489    Replace the CALL_PLACEHOLDER with an appropriate insn chain.  */
 490
 491 void
 492 optimize_sibling_and_tail_recursive_calls ()
 493 {
 494   rtx insn, insns;
 495   basic_block alternate_exit = EXIT_BLOCK_PTR;
 496   int current_function_uses_addressof;
 497   int successful_sibling_call = 0;
 498   int replaced_call_placeholder = 0;
 499   edge e;
 500
 501   insns = get_insns ();
 502
 503   /* We do not perform these calls when flag_exceptions is true, so this
 504      is probably a NOP at the current time.  However, we may want to support
 505      sibling and tail recursion optimizations in the future, so let's plan
 506      ahead and find all the EH labels.  */
 507   find_exception_handler_labels ();
 508
 509   /* Run a jump optimization pass to clean up the CFG.  We primarily want
 510      this to thread jumps so that it is obvious which blocks jump to the
 511      epilouge.  */
 512   jump_optimize_minimal (insns);
 513
 514   /* We need cfg information to determine which blocks are succeeded
 515      only by the epilogue.  */
 516   find_basic_blocks (insns, max_reg_num (), 0);
 517   cleanup_cfg ();
 518
 519   /* If there are no basic blocks, then there is nothing to do.  */
 520   if (n_basic_blocks == 0)
 521     return;
 522
 523   /* Find the exit block.
 524
 525      It is possible that we have blocks which can reach the exit block
 526      directly.  However, most of the time a block will jump (or fall into)
 527      N_BASIC_BLOCKS - 1, which in turn falls into the exit block.  */
 528   for (e = EXIT_BLOCK_PTR->pred;
 529        e && alternate_exit == EXIT_BLOCK_PTR;
 530        e = e->pred_next)
 531     {
 532       rtx insn;
 533
 534       if (e->dest != EXIT_BLOCK_PTR || e->succ_next != NULL)
 535         continue;
 536
 537       /* Walk forwards through the last normal block and see if it
 538          does nothing except fall into the exit block.  */
 539       for (insn = BLOCK_HEAD (n_basic_blocks - 1);
 540            insn;
 541            insn = NEXT_INSN (insn))
 542         {
 543           /* This should only happen once, at the start of this block.  */
 544           if (GET_CODE (insn) == CODE_LABEL)
 545             continue;
 546
 547           if (GET_CODE (insn) == NOTE)
 548             continue;
 549
 550           if (GET_CODE (insn) == INSN
 551               && GET_CODE (PATTERN (insn)) == USE)
 552             continue;
 553
 554           break;
 555         }
 556
 557       /* If INSN is zero, then the search walked all the way through the
 558          block without hitting anything interesting.  This block is a
 559          valid alternate exit block.  */
 560       if (insn == NULL)
 561         alternate_exit = e->src;
 562     }
 563
 564   /* If the function uses ADDRESSOF, we can't (easily) determine
 565      at this point if the value will end up on the stack.  */
 566   current_function_uses_addressof = sequence_uses_addressof (insns);
 567
 568   /* Walk the insn chain and find any CALL_PLACEHOLDER insns.  We need to
 569      select one of the insn sequences attached to each CALL_PLACEHOLDER.
 570
 571      The different sequences represent different ways to implement the call,
 572      ie, tail recursion, sibling call or normal call.
 573
 574      Since we do not create nested CALL_PLACEHOLDERs, the scan
 575      continues with the insn that was after a replaced CALL_PLACEHOLDER;
 576      we don't rescan the replacement insns.  */
 577   for (insn = insns; insn; insn = NEXT_INSN (insn))
 578     {
 579       if (GET_CODE (insn) == CALL_INSN
 580           && GET_CODE (PATTERN (insn)) == CALL_PLACEHOLDER)
 581         {
 582           int sibcall = (XEXP (PATTERN (insn), 1) != NULL_RTX);
 583           int tailrecursion = (XEXP (PATTERN (insn), 2) != NULL_RTX);
 584           basic_block call_block = BLOCK_FOR_INSN (insn);
 585
 586           /* alloca (until we have stack slot life analysis) inhibits
 587              sibling call optimizations, but not tail recursion.
 588              Similarly if we use varargs or stdarg since they implicitly
 589              may take the address of an argument.  */
 590           if (current_function_calls_alloca
 591               || current_function_varargs || current_function_stdarg)
 592             sibcall = 0;
 593
 594           /* See if there are any reasons we can't perform either sibling or
 595              tail call optimizations.  We must be careful with stack slots
 596              which are live at potential optimization sites.  ?!? The first
 597              test is overly conservative and should be replaced.  */
 598           if (frame_offset
 599               /* Can't take address of local var if used by recursive call.  */
 600               || current_function_uses_addressof
 601               /* Can't if more than one successor or single successor is not
 602                  exit block.  These two tests prevent tail call optimization
 603                  in the presense of active exception handlers.  */
 604               || call_block->succ == NULL
 605               || call_block->succ->succ_next != NULL
 606               || (call_block->succ->dest != EXIT_BLOCK_PTR
 607                   && call_block->succ->dest != alternate_exit)
 608               /* If this call doesn't end the block, there are operations at
 609                  the end of the block which we must execute after returning. */
 610               || ! call_ends_block_p (insn, call_block->end))
 611             sibcall = 0, tailrecursion = 0;
 612
 613           /* Select a set of insns to implement the call and emit them.
 614              Tail recursion is the most efficient, so select it over
 615              a tail/sibling call.  */
 616           if (sibcall)
 617             successful_sibling_call = 1;
 618
 619           replaced_call_placeholder = 1;
 620           replace_call_placeholder (insn,
 621                                     tailrecursion != 0
 622                                       ? sibcall_use_tail_recursion
 623                                       : sibcall != 0
 624                                          ? sibcall_use_sibcall
 625                                          : sibcall_use_normal);
 626         }
 627     }
 628
 629   if (successful_sibling_call)
 630     {
 631       rtx insn;
 632
 633       /* A sibling call sequence invalidates any REG_EQUIV notes made for
 634          this function's incoming arguments.
 635
 636          At the start of RTL generation we know the only REG_EQUIV notes
 637          in the rtl chain are those for incoming arguments, so we can safely
 638          flush any REG_EQUIV note.
 639
 640          This is (slight) overkill.  We could keep track of the highest
 641          argument we clobber and be more selective in removing notes, but it
 642          does not seem to be worth the effort.  */
 643       purge_reg_equiv_notes ();
 644
 645       /* A sibling call sequence also may invalidate RTX_UNCHANGING_P
 646          flag of some incoming arguments MEM RTLs, because it can write into
 647          those slots.  We clear all those bits now.
 648
 649          This is (slight) overkill, we could keep track of which arguments
 650          we actually write into.  */
 651       for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
 652         {
 653           if (GET_CODE (insn) == NOTE)
 654             {
 655               if (NOTE_LINE_NUMBER (insn) == NOTE_INSN_FUNCTION_BEG)
 656                 break;
 657             }
 658           else if (INSN_P (insn))
 659             purge_mem_unchanging_flag (PATTERN (insn));
 660         }
 661     }
 662
 663   /* There may have been NOTE_INSN_BLOCK_{BEGIN,END} notes in the
 664      CALL_PLACEHOLDER alternatives that we didn't emit.  Rebuild the
 665      lexical block tree to correspond to the notes that still exist.  */
 666   if (replaced_call_placeholder)
 667     reorder_blocks ();
 668
 669   /* This information will be invalid after inline expansion.  Kill it now.  */
 670   free_basic_block_vars (0);
 671 }